Low-temperature lubricating greases

ABSTRACT

GREASE COMPOSITIONS COMPRISING (A) A LUBRICATING OIL COMPOSITION WHICH COMPRISED A BLEND OF SYNTHETIC ALARYL HYDROCARBON LUBRICANT AND A SYNERGISTIC AMOUNT OF A MINERAL LUBRICATING OIL AND (B) A GREASE-FORMING AMOUNT OF A CONVENTIONAL GREASE-FORMING AGENT, SUCH AS MODIFIED BENTONITE. THE GREASE HAVE GOOD TO EXCELLENT VISCOSITY PROPERITIES AT TEMPERATURES AS LOW AS -40 TO -62* F., THUS RENDERING THEM USEFUL AT THESE TEMPERATURES. USE OF A BLEND OF SYNTHETIC ALKARYL HYDROCARBON LUBRICANT AND A MINERAL LUBRICATING OIL, AS COMPARED TO USE OF A SYNTHETIC ALKARYL HYDROCARBON LUBRICANT ALONE, RESULTS IN A GREASE COMPOSITION HAVING IMPROVED LOW TEMPERATURE VISCOSITY PROPERTIES, WHICH IS ALSO LOWER COST.

United States Patent O 3,785,974 LOW-TEMPERATURE LUBRICATING GREASES William P. Scott, Ponca City, Okla, assignor to Continental Oil Company, Ponca City, Okla.

No Drawing. Filed May 17, 1972, Ser. No. 254,021 Int. Cl. (310m 7/20 US. Cl. 252-28 13 Claims ABSTRACT OF THE DISCLOSURE Grease compositions comprising (a) a lubricating oil composition which comprises a blend of synthetic alkaryl hydrocarbon lubricant and a synergistic amount of a mineral lubricating oil and (b) a grease-forming amount of a conventional grease-forming agent, such as modified bentonite. The greases have good to excellent viscosity properties at temperatures as low as 40 to 62 F., thus rendering them useful at these temperatures. Use of a blend of synthetic alkaryl hydrocarbon lubricant and a mineral lubricating oil, as compared to use of a synthetic alkaryl hydrocarbon lubricant alone, results in a grease composition having improved low temperature viscosity properties, which is also lower cost.

CROSS-REFERENCE TO RELATED APPLICATIONS Commonly assigned application Ser. No. 254,015, filed the same date as the present application, wherein the inventors are Robert A. Krenowicz and William P. Scott, discloses and claims a lubricating oil composition comprising a synthetic alkaryl lubricant and a synergistic amount of a mineral lubricating oil.

BACKGROUND A need for greases having good low temperature properties has existed for many years. The discovery of oil in Arctic regions (e.g., northern Canada and the North Slope of Alaska) has intensified this need due to the increasing amount of machinery and equipment which is exposed to colder climates.

The present invention is concerned with grease compositions which have good to excellent viscosity properties at temperatures in the range of 40 to 62 F. Because of their excellent low temperature viscosity properties, the greases are pumpable at temperatures of -40 to -62 F. In fact, the greases can be dispensed with ordinary handtype grease guns at these temperatures.

PRIOR ART The use of diesters and other non-hydrocarbon lubricants to prepare greases has been known for many years. Greases prepared from these materials are relatively expensive.

US. Pat. No. 3,173,965 teaches that dialkylbenzenes have good low temperature properties and that greases can be prepared from these materials.

British Pat. No. 1,144,615 teaches blends of synthetic hydrocarbon lubricants and mineral lubricating oils as hydraulic oils. It does not, however, teach the use of such blends to prepare greases.

To my knowledge, there are no teachings that a synergistic effect is present in greases prepared from mixtures of synthetic alkaryl hydrocarbon lubricants and mineral lubricants.

BRIEF SUMMARY OF THE INVENTION Broadly stated, my invention is directed to a lubricating grease comprising (a) a lubricating oil composition which comprises a synthetic alkaryl hydrocarbon lubricant and a synergistic amount, in the range of about 3,785,974 Patented Jan. 15, 1974 DETAILED DESCRIPTION Definition of synergistic amount and synergistic effect: The term synergistic effect refers to an unexpectedly improved property in the grease composition due to the use of a combination of materials. The property measured is better than that obtained when only one of the materials is used.

The term synergistic amount, as used herein and in the claims, refers to that amount of the mineral lubricating oil which when added to the synthetic alkaryl hydrocarbon lubricant produces an improvement in one or more properties of the grease composition. For example, a grease composition prepared from a blend of 100 parts synthetic hydrocarbon lubricant and 25 to 67 parts of a naphthenic oil, has a better apparent viscosity at --40 to 62 F. than does a grease composition prepared from either oil alone.

Synthetic hydrocarbon alkaryl lubricant The synthetic hydrocarbon alkaryl lubricant used in my invention is characterized as containing a major amount of di-n-long-chain alkaryls and a minor, but significant, amount of trialkyl-substituted tetrahydronaphthalenes.

In the di-n-long-chain alkaryls the long chain alkyl groups contain from about 6 to about 18 carbon atoms, more suitably from about 10 to about 15 carbon atoms and preferably from about 11 to about 14 carbon atoms. The aryl moiety is phenyl, tolyl or xylyl, but preferably is phenyl. Thus, the preferred di-n-long-chain alkaryls are di-n-alkylbenzene wherein the alkyl groups conform to the long-chain alkyl definition of the foregoing. The term n-alkylbenzenes as used herein refers to benzenes containing a substantially straight-chain alkyl group, wherein, preferably, at least percent of the alkyl substituents are bonded to the benzene nucleus through a secondary carbon atoms of the respective alkyl group. While I prefer the term n-alkylbenzenes other terms such as linear alkylbenzenes or straight-chain alkylbenzenes are equally descriptive.

The trialkyl-substituted tetrahydronaphthalenes can be represented by the formula H its-( L wherein R and R contain from 1 to about 13 carbon atoms each, with the sum of R and R being from about;

6 to about 14 and R and R contain from 1 to about 16 carbon atoms with the sum of R and R being from about 9 to about 17. The alkyl groups, R R R and R are straight-chain.

The trialkyl-substituted tetrahydronaphthalenes have the same boiling range as the di-n-alkylbenzenes. In addition, they have approximately the same molecular weight.

In addition to the di-n-long-chain alkaryls and trialkylsubstituted tetrahydronaphthalenes the synthetic hydrocarbon alkaryl lubricant can contain minor amounts of miscellaneous alkyl aromatic compounds.

The synthetic hydrocarbon alkaryl lubricant composition has the following composition:

Percent Component: by weight Di-n-long-chain alkaryls 61 to 92. Trialkyl-substituted tetrahydronaphthalenes to 30. Miscellaneous alkyl aromatics Less than 15. Preferably Less than 10.

The materials are also characterized as having the following properties:

Viscosity index 80 to 116.

Pour point, F. 40 to 80 Molecular Weight range 350 to 526. Preferably 375 to 480.

The synthetic hydrocarbon alkaryl lubricants can be prepared by any of several methods. They can be prepared by alkylating benzene and tetrahydronaphthalene and blending the resulting product. Also, they can be prepared by alkylating a mixture of mono-n-alkylbenzenes and dialkyl-substituted tetrahydronaphthalenes with a suitable alkylating agent. A particularly suitable method of preparing the synthetic hydrocarbon alkaryl lubricants is by the disproportionation of a mono n alkylbenzene rich feedstock using HF-BF aluminum bromide 01' aluminum chloride as the catalyst.

While we are describing in detail the disproportionation method of preparing the synthetic hydrocarbon lubricant, it is to be understood that any composition having the compositions and physical properties described in the foregoing is suitable for use in my invention.

Suitable mono-n-alkylbenzenes are those containing from about 6 to about 18 carbon atoms in the alkyl groups. Preferably, the alkyl groups of the monon-alkylbenzenes contain from about 10 to about carbon atoms. The term n-alkylbenzenes has been defined in the foregoing.

A particularly suitable material for use in preparing the disproportionated product is a composition, containing a substantial amount of mono-n-alkylbenzenes conforming to the foregoing description, produced in accordance With the process of U.S. Pat. No. 3,316,294. Briefly, U.S. Pat. No. 3,316,294 relates to a process of preparing a detergent alkylate, wherein the process comprises the following steps, broadly stated: (a) separating a fraction of substantially straight-chain C -C hydrocarbons from a petroleum distillate substantially free of olefins and containing said straight-chain hydrocarbons together with non-straight chain hydrocarbons, (b) chlorinating said fraction to the extent whereby between about 10 and about 35 mole percent of the straight-chain hydrocarbons present are substantially only mono-chlorinated, (c) alkylating an aromatic compound, e.g. benzene, with the chlorination product of step (b) in the presence of an alkylation catalyst, and (d) recovering from the reaction mass, by distillation, a fraction consisting essentially of mono-n-alkylbenzenes.

While U.S. Pat. No. 3,316,294 concerns a process which can use C to C hydrocarbons the present invention uses hydrocarbons which can contain from about 6 to about 18 carbon atoms. The C -C hydrocarbons can be obtained by a modification of the process described as step (a) of U.S. Pat. No. 3,316,294. In addition, other means of obtaining a C -C hydrocarbon fraction will be apparent to those skilled in this art. When it is desired to use an alkylbenzene containing 10 to 15 carbon atoms in the alkyl group, this selection can be made either in the initial feedstock or by fractionation of the alkylbenzene product.

Process conditions for disproportionation reaction Preferably, the disproportionation reaction is conducted using aluminum chloride as the catalyst. The amount of the catalyst which is used can vary from about 0.1 weight percent to about 10 Weight percent'based on the mono-n-alkylbenzene starting material. Preferably, the amount of catalyst is from about 0.5 weight percent to about 5 weight percent.

In some cases it is desirable to use a proton-donor promoter with the aluminum chloride catalyst. Suitable promoters include any material which, when added to the catalyst, yields a proton. Preferred promoters are hydrogen chloride and water. The amount of promoter is typically about 4 weight percent based on the weight of the catalyst employed. It should be emphasized that anyone skilled in this art can readily determine the necessity of using a promoter and the amount of promoter, if used.

The disproportionation process, suitably, is conducted at a temperature of from about 20 C. to about C. Since maximum yields of the di-n-alkylbenzenes are obtained at temperatures between about 65 C. and 120 C., these temperatures are preferred.

Following the reaction, the reaction mass is distilled in order to remove the benzene, paraffins and unreacted mono-n-alkylbenzenes. The desired product is the disproportionated material distilling in the range of about C. to about 300 C. at 5 mm. Hg. This material has an average molecular weight in the range of about 350 to about 470. In conducting the distillation, more suitably the lower cut point is C. at 5 mm. Hg. Preferably, the lower cut point is 197 C. at 5 mm. Hg.

In some instances the desired fraction is obtained by distilling from the disproportionated product a select fraction or overhead amounting to from about 10 to about 90 percent of the disproportionate.

The term mineral lubricating oil, as is well known, refers to materials resulting from the refining of crude petroleum. Particularly suitable mineral lubricating oils for preparing my greases are pale oils and naphthenic oils. While I believe the terms pale oils and naphthenic oils to be well-known to those skilled in this art, in order to render our disclosure more complete a brief discussion will be provided concerning these materials.

In the refining of petroleum the crude petroleum is subjected to a distillation which produce straight-run gasoline, kerosine, and gas oil. The residue of reduced crude is used to prepare the lubricating oil. Both naphthenic and pale oil are the distillate fraction Whereas the bottom fraction is used to prepare bright stocks. Conventionally, the pale oils and naphthenic oils are subjected to further treatment to improve color and reduce the wax content thereof.

While both pale oils and naphthenic oils are distillate oils, they differ in many respects such as type of crude petroleum from which they are derived, chemical composition and physical properties. Naphthenic oils have a greater amount of aromatics, lower viscosity indexes, and lower pour points than do the pale oils. Anyone skilled in this art can distinguish pale oils and naphthenic oils on the basis of the following properties: viscosity index and pour point.

The naphthenic oils are preferred in my invention since they provide a synergistic effect over a broader composition range.

In order to make my disclosure of suitable mineral lubricating oils more complete the following book is made a part of my disclosure: Petroleum-Prehistoric to Petrochemicals; G. A. Purdy; Copp Clark Publishing Company, Vancouver, Toronto, Montreal, Canada (1958). The following pages thereof are especially pentinent: 225, 226, 227, 228, 231, 234, 242 and 373.

Greases of my invention Grease-forming agents: Any of the conventional greaseforming agents can be used to prepare the greases of my invention. As is well known, most of the greases of commerce use metal soaps prepared by saponifying fats and oils of animal, vegetable or marine origin, either alone or in combination. In addition to the preceding, other saponifiable materials include rosin oil, naphthenic acids, sulfonic acids, synthetic fatty acids, montan wax and wool grease. The metals of the grease-forming agent can be aluminum, barium, calcium, lithium, sodium, magnesium, lead or strontium.

In addition to the preceding, various types of chemically or physically modified clays have been used as grease-forming agents. Examples of suitable clays for modification and subsequent use as a grease-forming agent include bentonite, saponite, attapulgite, zeolite and fullers earth. Of the modified clays, the modified bentonites are preferred as the grease-forming agent. It is believed that the term modified bentonite is now well-understood in the grease art. The book by C. J. Boner entitled Manufacture and Application of Lubricating Greases (Reinhold, New York-1954), on pages 724 and 725, describes modified bentonites.

The more suitable grease-forming agents for use in my invention are the modified clays, particularly modified bentonite, and lithium fatty acid soaps.

Where it is desired to prepare grease compositions having low viscosities at extremely low temperatures (i.e., -50 to 65 F.), the modified bentonites are preferred as the grease-forming agent.

Amount of grease-forming agent Knowing that the lubricating oil compositions of my invention can be used as a base oil for preparing greases, the required amounts of grease-forming agent can be readily determined. In order to make my disclosure more complete, I include the following: Suitably, the amount of grease-forming agent, used in the greases of my invention, is in the range of about 1 to about 43 parts per 100 parts of lubricating oil composition. Preferably, on the same basis, the amount of grease-forming agent is in the range of about 5 to about 11 parts. As is well known in the grease art, varying the amount of grease-forming agent affects the consistency of the grease product.

Use of additives Various additives, such as rust inhibitors, oxidation inhibitors, lubricity agents, extreme pressure agents, stringiness agents, and the like, may be added to the grease of my invention.

Definition of synergistic amounts Parts per 100 parts of synthetic hydrocarbon lubricant Suitable -100 Preferred 25-67 Advantages of my invention Where grease compositions are desired having improved flow properties at extremely low temperatures (i.e., 50 to 62 F.), a blend of synthetic alkaryl hydrocarbon and naphthenic or pale oil, with modified bentonite as the grease-forming agent, would be desired.

Where grease compositions are desired having improved flow properties in the range of -20 to 40 F., a blend of synthetic alkaryl hydrocarbon and naphthenic or pale oil, with a lithium fatty acid soap for the greaseforming agent, could be used.

From the apparent viscosities shown in the examples it is readily apparent to anyone skilled in this art that the greases of my invention are pumpable at temperatures as low as 62 F. In fact, it is apparent that the viscosities are such that the greases can be dispensed with an ordinary hand gun at the temperatures shown.

In order to disclose the nature of the present invention still more clearly, the following examples, both illustrative and comparative, will be given. It is to be understood, however, that the invention is not to be limited to the specific conditions or details set forth in these examples except insofar as such limitations are specified in the appended claims.

Materials used in examples Di-n-alkylbenzenes 69.3 Trialkyl-substituted tetrahydronaphthalenes 22.3 Indenes 2.9 Diphenylalkanes 1.6

The components of the composition were in a molecular weight range of 442 to 470.

The composition had the following physical properties:

Miscellaneous compounds Pour point, F. --60 Viscosity index 110 Viscosity, cs., at-

210 F. 4.94 100 F. 28.22 -40 F. 9,5400

Mineral lubricating oils: The naphthenic oil and the pale oil used had the following properties:

Viscosity, cs. at

Pour oint v1. p O F.

Naphthenic oil Pale oil 1 1 Commonly referred to as pale on."

EXAMPLE 1 This example illustrates the effect on viscosity at low temperatures of greasese prepared using blends of the synthetic hydrocarbon and pale oil or naphthenic oil. The greases in this example used as the thickening agent, a modified bentonite, which was Nykon 77, available from the Baroid Division of National Lead Company, and which contains a small amount of sodium nitrite for rust inhibition. In addition to grease-forming agent and base lubricating oils, the greases contained small amounts of conventional grease additives such as oxidation inhibitor and film strength additives.

The test apparatus used in this example consisted basically of a 20-foot coil of 0.3154 inch I.D. copper tubing immersed in a refrigerated bath. A 24-foot pre-cooler coil of inch copper tubing was attached to the 20-foot coil,

the pre-cooler coil also being immersed in the refrigerator bath. A variable speed gear pump (1. gallon per hour) was attached between the grease reservoir and the pre-cooler coil. A pressure gauge was attached at the junction of the pre-cooler coil and the 20-foot test coil. The gear pump was force-fed "by putting air pressure on the grease reservoir to prevent cavitation. This pressure did not influence the grease flow rate in the positive displacement gear pump. The grease flow rate in cubic inches per minute versus pressure drop per foot of test pipe was obtained. Apparent viscosities were obtained using Poiseuilles equation. This method of handling lubricating grease flow data is well known in the art and described in detail in ASTM Test Method D 1092.

The composition of the various greases, penetration data, and apparent viscosity data are shown in Tables I-A and IB.

TABLE IA.GREASE COMPOSITION While particular embodiments of the invention have been described, it will be understood, of course, that the inventionis not limited thereto, since many modifications thenic oil A, 35.51% (60:40 ratio).

TABLE IB.PROPERTIES OF GREASE COMPOSITIONS OF TABLE I-A Apparent vis- Strokes cosity, poises Number Base oil 60 10, 000 -40 F. -62 F.

A 100% synthetic hydrocarbon 330 350 1 13,000 1 25,000 2 7, 400 2 15, 500 B 100% 80 pale oil 320 340 1 17, 500 1 50, 000 C 100% naphthenic oil A 352 380 1 1g,

2 D 60%1syirithetic hydrocarbon-40% 80 330 350 1 12, 000 1 21, 000

pa e o E 80% synthetic hydrocarbon-% naph- 330 343 l 12, 000 1 18, 000 naphthenic oil A. 1 6, 600 3 12, 000 F 60% synthetic hydrocarbon-% naph- 342 345 1 9, 000 l 19, 500 naphthenic oil A. a 5, 200 8 13, 500

1 At 0.5 see. shear rate. 1 At 1.0 seer shear rate. 8 At 1.0 sec.- Shear rate and -60 F. 4 Too viscous to be measurable at this temperature.

EXAMPLE 2 This example illustrates greases using a lithium fatty acid soap as the thickening agent and blends of synthetic hydrocarbon lubricant and naphthenic oil as the base oil. The example shows that using up to 40% naphthenic oil provides greases having substantially the same, or slightly better, viscosity properties than present in greases using 100% synthetic hydrocarbon lubricant.

The grease-forming agent was lithium 12-hydroxy, stearate and naphthenic oil A was used. As in Example 1, the greases contained small amounts of conventional grease additives.

The composition of the various greases, penetration data, and apparent viscosity data are shown in Tables II-A and II-B.

TABLE IIA.-GREASE COMPOSITION USING LITHIUM 12 HYDROXY STEARATE AS THICKENER thenlc oil A, 44.10%

may be made; and it is, therefore, contemplated to cover by the appended claims any such modifications as fall within the true spirit and scope of the invention.

The invention having thus been described, what is claimed and desired to be secured by Letters Patent is:

1. A lubricating grease composition comprising: (a) a lubricating oil composition which consists essentially of a synthetic alkaryl hydrocarbon lubricant and a synergistic amount, in the range of about 10 to about parts per 100 parts of synthetic alkaryl hydrocarbon lubricant, of a mineral lubricating oil selected from the group consisting of pale oils and naphthenic oils and ('b) a grease-forming amount, in the range of about 1 to about 43 parts per 100 parts of lubricating oil composition, of a greaseforming agent selected from the group consisting of modified clays and lithium fatty acid soaps, said synthetic alkaryl hydrocarbon being characterized as containing from about 61 to about 92 percent by weight di-n-longchain alkaryls, wherein the long-chain alkyl groups contain from about 6 to about 18 carbon atoms and the aryl moiety is phenyl, tolyl, or xylyl, and from about 5 to about 30 percent by weight trialkyl-substituted tetrahydro- TABLE IIB.PROPERTIES OF GREASE COMPOSITIONS OF TABLE II-A Pene- Apparent vi stiosity, poises,

1 At 1.0 sec.2 shear rate. 1 This oil shows slight synergistic efiect at 20 and 30 F a This oil shows synergistic efiect at 20, 30 and 40 F.

4 This oil shows that the maximum effective amount has been passed and the grease IS approaching the properties of one prepared from 100% naphthenic oil.

naphthalenes, said synthetic hydrocarbon lubricant having the following physical properties:

Viscosity index 80 to 116. Pour point, F. -40 to -80. Molecular weight 350 to 526.

2. The grease composition of claim 1 wherein the di-nlong-chain alkaryls are di-n-alkylbenzenes, the alkyl groups of which contain about 10 to about 15 carbon atoms.

3. The grease composition of claim 2 wherein the mineral lubricating oil is a naphthenic oil.

4. The grease composition of claim 3 wherein the grease-forming agent is a modified clay.

5. The grease-forming composition of claim 4 wherein the grease-forming agent is modified bentonite.

6. The grease composition of claim 3 wherein the grease forming agent is a lithium fatty acid soap.

7. A lubricating grease composition comprising: (a) a lubricating oil composition which consists essentially of a synthetic alkaryl hydrocarbon lubricant and a synergistic amount, in the range of about 25 to about 67 parts per 100 parts of synthetic alkaryl hydrocarbon lubricant, of a mineral lubricating oil selected from the group consisting of pale oils and naphthenic oils, and (b) a grease-forming amount, in the range of about 1 to about 43 parts per 100 parts of lubricating oil composition, of a grease-forming agent selected from the group consisting of modified clays and lithium fatty acid soaps, said synthetic alkaryl hydrocarbon being characterized as containing from about 61 to about 92. percent by weight di-n-long-chain alkaryls, wherein the long-chain alkyl groups contain from about 6 to about 18 carbon atoms and the aryl moiety is phenyl, tolyl, or xylyl, and from about to about 30 percent by weight trialkyl-substituted tetrahydronaphthalenes, said 10 synthetic hydrocarbon lubricant having the following physical properties:

Viscosity index to 116. Pour point, F 40 to 80. Molecular weight 350 to 52-6.

8. The grease composition of claim 7 wherein the mineral lubricating oil is a naphthenic oil.

9. The grease composition of claim 8 wherein in the synthetic alkaryl hydrocarbon lubricant the di-n-longchain alkaryls are di-n-alkylbenzenes, the alkyl groups of which contain about 10 to about 15 carbon atoms.

10. The grease composition of claim 9 wherein the grease-forming agent is present in an amount in the range of about 5 to about 11 parts per parts of lubricating oil composition.

11. The grease composition of claim 10 wherein the grease-forming agent is a modified clay.

12. The grease composition of claim 11 wherein the grease-forming agent is modified 'bentonite.

13. The grease composition of claim 10 wherein the grease-forming agent is a lithium .fatty acid soap.

References Cited UNITED STATES PATENTS 3,544,472 12/1970 Bray et al 252-59 3,173,965 3/1965 Pappas ct al 260-67l B 1,815,022 7/1931 Davis 252-59 DANIEL E. WYMAN, Primary Examiner W. H. CANNON, Assistant Examiner US. Cl. X.R. 252-41, 59 

